830 Proceedings of Royal Society of Edinburgh. [sess. 
composed. Most metals lose at 100° C. about thirty per cent, of 
their conductivity at 0° C. Yet they vary very much regarding 
their conductivity, and one consequently chooses the metal 
according as one wants a grating of low or of high resistance for 
a given cross section and length. 
( Issued separately July 10 , 1905 .) 
